France is planning to repatriate more than 100 Isil suspects from Syria amid fears they could lose track of them after US troops withdraw from the war-torn country.

Some 130 Isil suspects being held in custody by Syrian Democratic Forces (SDF) in prisons across northern Syria are to be sent back within the next few weeks, according to French channel BFMTV.

"All those who will return to France will be entrusted to the judges. The judge will decide that it will be necessary to put them in prison," Christophe Castaner, France's Interior Minister, told BFMTV.

"The Americans are disengaging from Syria… There are now people in prison who are being held because the Americans are there and who are going to be released… They'll want to return to France."

Among those in SDF custody are a number of senior French Isil leaders including Adrien Guihal, a Muslim who was part of the infamous Artigat network that masterminded several attacks in France, including one in Nice which killed 87 people.

Such a decision would make France the first European country to take back citizens arrested on suspicion of links to Islamic State of Iraq and the Levant (Isil).

Only the US, Lebanon, Russia, Indonesia and Sudan, have so far agreed to repatriate their nationals.

Thousands of other foreign Isil members in SDF detention remain in limbo, including six British male Isil suspects, seven women and 12 of their children.

Britain and other countries have expressed reluctance to take back those with links to Isil, citing fears they represent a security threat.

They have also indicated concern about evidential and legal challenges that would prevent them from prosecuting returning extremists.

Alexanda Kotey and El Shafee Elsheikh, the two so-called Beatles jihadists, have had their UK citizenship revoked.

The Kurdish-led SDF has been supported on the ground by US special forces, as well as British and French.

However, US President Donald Trump announced he was to bring home 2,000 American troops within months.

Following the announcement, Turkey, which considers Kurdish militants fighting with the SDF to be terrorists, threatened to carry out an assault on Kurdish-held areas near their shared border.

The Kurds warned they may not be able to keep jihadists inside their jails.

There also remains the possibility that the SDF, which has begun talks with the Bashar al-Assad government, could hand over prisoners to the regime.

Tens of thousands have disappeared inside government prisons, where many were executed without trial.

"Reversal of French policy with respect to Isil suspects held in northern Syria, as France finally agrees to take its nationals back," Nadim Houry, director of the counterterrorism programme at Human Rights Watch, tweeted. "This may be unpopular but it is the right thing to do. Prosecute those who committed crimes, reintegrate children."

The plan provoked outrage on the right. Eric Ciotti, a conservative MP from the main opposition party, the Republicans, said: "The place of jihadists who betrayed our nation and fought our civilisation is no longer in France. Let them be judged in Iraq or Syria."